Without limiting the scope of the invention, its background is described in connection with elastomeric bearings.
U.S. Pat. No. 9,334,048, issued to Burnett, is entitled, “Elastomeric bearing having tapered layers”, teaches a rotor hub for an aircraft that includes a yoke, a rotor mast, and a hub spring assembly. The hub spring assembly includes an upper outer member, an upper inner member, and an upper spring member having a plurality of elastomeric layers and shim layers sandwiched between the upper outer member and the upper inner member, the shim layers being tapered such that a thickness of each shim layer is smaller at a side portion as compared to the thickness of the shim at a center portion.
U.S. Pat. No. 9,085,357, issued to Davis and Stamps, is entitled, “Rotor hub bearing system”, teaches a bearing system configured for treating and reacting dynamic loading within a rotor hub of rotorcraft. The bearing system includes an outer member having a plurality of alternating outer elastomeric layers and shim layers. The outer member has an inboard surface configured for bonding to an inboard bearing support, and the outer member has an outboard surface configured for bonding to an outboard bearing support. The bearing system has an inner member bonded to an interior surface of the outer member. The inner member can include a rigid inner core, as well as a plurality of elastomeric layers and shim layers configured to react torsional movements of the rotor blade.